U.S. Pat. No. 3,929,316 dated Dec. 30, 1975 is directed to a non-floating pressed in seat for a gate valve. An annular deformable seal, preferably formed of Teflon, is positioned in opposed grooves in the back face of the seat and the adjacent body surface defining the body recess in which the seat is pressed. The seal and groove are sized in order to provide a face-to-face abutting contact between the seat and the body without any portion of the seal being gripped between the opposed faces of the seat and valve body. The pressed-in seat provides a fluid-tight barrier to fluid pressure tending to seep outwardly past the seal. Thus, the area of the seat exposed to fluid pressure is minimized and a non-floating seat is provided.
In order to easily press the seat in the body recess without any galling of contacting surfaces a lubricant is normally placed on the outer peripheral surface of the seat and/or the inner peripheral contacting surface of the recess. The insertion of the seat with tight tolerances sometimes results, particularly when a relatively large amount of lubricant is positioned on the adjacent peripheral surfaces, in the forcing of the lubricant along the inner peripheral surface of the recess and along a portion of the back face of the seat adjacent the inner peripheral surface defining the recess which sometimes prevents full metal-to-metal abutting contact with the valve body. If the seal is not fully seated, fluid pressure behind the seat may urge the seal outwardly out of its recess.